Switch breaker

ABSTRACT

A circuit breaker is described wherein an automatic overload current circuit interrupting feature is combined with a manual switching feature. A latch plate has an abutment ledge surface for contact with a bimetallic element. The abutment ledge surface has a predetermined latch angle relative to a plane which is normal to the axis of movement of the latch plate. The angle is selected to form a latch which may be manually overcome by movement of the latch plate against the bimetallic element to force the bimetallic element to slip off the abutment ledge surface. A range and preferred values of the latch angle are described.

United States Patent [191 Riendeau [4 Aug. 28, 1973 SWITCH BREAKER William P. Riendeau, Leonardtown, Md.

Assignee: Aiken Industries, Incorporated, New

York, N.Y.

Filed: Feb. 22, 1972 Appl. No.: 228,100

Inventor:

References Cited UNITED STATES PATENTS 9/1954 lngwersen 337/66 11/1959 Arey 337/72 X Primary Examiner-Remand A. Gilheany Assistant Examiner-A. T. Grimley Attorney-Louis Reens [5 7] ABSTRACT A circuit breaker is described wherein an automatic overload current circuit interrupting feature is combined with a manual switching feature. A latch plate has an abutment ledge surface for contact with a bimetallic element. The abutment ledge surface has a predetermined latch angle relative to a plane which is normal to the axis of movement of the latch plate. The angle is selected to form a latch which may be manually overcome by movement of the latch plate against the bimetallic element to force the bimetallic element to slip off the abutment ledge surface. A range and preferred values of the latch angle are described.

8 Claims, 3 Drawing Figures SWITCH BREAKER BACKGROUND OF THE INVENTION This invention relates to a circuit breaker having a manual switch function and automatic circuit interruption.

Circuit breakers with manual switching are well known in the art. Note for example, the U.S. Pat. to Ingwersen, Nos. 2,838,635 and 2,821,086 wherein movable cam elements provide a detent force to normally retain movable contacts on a plunger assembly in a switch closing position. When the plunger assembly is manually actuated, the cam elements are moved to open the switch and seat the movable contacts on a shoulder under action by a spring. Another type of manual switching circuit breaker is disclosed in the U.S. Pat. to Arey, No. 2,912,546. With particular reference to FIG. in the Arey patent, a spring latch member engages an angled abutment surface on a plunger assembly to maintain movable contacts in a switch closing position. A manual pull on the plunger overcomes the spring latch member to open the switch.

A disadvantage with the described prior art switchbreakers resides in the use of additional releaseoperative components to impart a manual override or switch opening capability. A switch breaker in accordance with the invention, however, dispenses with such additional release components to provide an advantageously simple practical device.

SUMMARY OF THE INVENTION In a switch-breaker formed in accordance with the invention, .a bimetallic element is located, during switch closure, in latching engagement with a latch plate. The bimetallic element seats on an inclined ledge of the latch plate which is mounted on a plunger. The plunger assembly moves along an axis and the ledge of the latch plate is precisely inclined relative to a plane which is normal to that axis. Circuit interruption or switch opening by separation of the bimetallic element from the ledge may then occur either by pulling on the plunger or, when an overload current has sufficiently heated the bimetallic element, by bending it away from the ledge.

A switch-breaker in accordance with the invention advantageously dispenses with components normally employed in prior art devices which provide both circuit breaking and manual switching functions.

It is, therefore, an object of the invention to provide a switch-breaker of simple design and which is capable of providing both manually switching functions and current overload protection with an economic and practical structure. These and other advantages and objects will become understood from the following description of a preferred embodiment described in conjunction with the drawings wherein FIG. 1 is a side-view in partial section of a mounted switch-breaker in accordance with the ivention;

FIG. 2 is a partial section of the switch-breaker of FIG. 1 taken along the line 2-2 in FIG. 1; and

FIG. 3 is an enlarged perspective view of elements employed to provide the switch function of the switchbreaker in accordance with the invention.

With reference to FIG. 1, a switch-breaker 10 is shown mounted on a wall 12. The switch-breaker 10 has a pair of terminals 14-14 which are respectively connected to a pair of stationary contacts 16-16 located on a housing 17 in a recess 18. A pair of movable contacts 19-19 are mounted on a U-shaped bimetallic element 20, which in turn is mounted for movement along an insulator plunger 22. In FIG. 1, the bimetallic element 20 is shown in a switch closure position with the lower segment 24 of bimetallic element 20 latched on a ledge 26 of a latch plate 28. Plunger 22 has an extension 30 protruding through wall 12 and an externally threaded bushing 32 for manual engagement and actuation. A nut 34 is threaded on bushing 32 to retain switch-breaker 10 on wall 12.

When the bimetallic element is latched on ledge 26, a main spring 36 pushes the entire plunger assembly up against stationary contacts 16-16 to close the switch and complete a circuit between terminals 14-14. A pair of springs 38-38, which are anchored to lower shoulders of plunger 22, are connected to bimetallic element 20 to provide a switch opening force when the bimetallic element moves off ledge 26.

These described components are well-known and commonly used as described in the lngwersen U.S. Pat. Nos. 2,831,066 and 2,694,122. The critical and advantageous inventive change resides in the particular orientation of ledge 26 and its operations with the bimetallic element 20 as more clearly illustrated in FIGS. 2 and 3.

Latch plate 28 is shown in FIG. 2 mounted in a recess 40 of plunger 22 with a rivet 42. A lip 44 projects inwardly towards an adjustment screw 46 in a manner as shown and described in Ingwersen 2,694,122. The lower ledge 26 of latch plate 28 projects outwardly for essentially transverse contact by edge 24 of bimetallic elements 20. Ledge 26 provides a seating surface 48 located in a latch plane 49 which bears an angle 45 relative to a plane 50. Plane 50 is transverse to the axis 42 along which plunger 22 is moved. The angle :15 in the embodiment of FIGS. 2 and 3 is about 30.

With a latch angle 46 of about 30, the plunger 22 may be moved in the direction of arrow 54, against the latched bimetallic element 20 to force the latter to slip off ledge 26. Upon unlatching, springs 38-38 shown in FIG. 1, open the switch and enable the bimetallic element to seat on shoulders 56-56 of plunger 22 as shown in dotted outline in FIG. 2.

A careful view of FIG. 4 in Ingwersen U.S. Pat. No. 2,694,122 illustrates an inclined ledge or abutment surface which also bears a slight angle relative to a plane transverse to the axis of movement of the plunger. Since the latch plate may be laterally adjusted by a screw to set the desired overload current, this slight incline, generally about 6 to 10, serves to enable the bimetallic element to move laterally away for all overload settings. In other words, without this slight incline overload setting adjustments made with the adjustment screw might trap the bimetallic element, which then could only unlatch with a destructive bending movement.

When the incline of the ledge of the latch plate is as small as needed for a circuit breaker such as described inlngsersen U.S. Pat. No. 2,694,122, the latching contact with the bimetallic element does not permit a manual release by pulling on the plunger. If such manual disengagement is attempted, the bimetallic element would be physically distorted.

On the other hand, when the incline of the ledge is increased to form a latch angle of about 20 in accordance with the invention, such physical distortion is avoided and a manual switch function is obtained. At the preferred latch angle 4: of about 30, a reliable distortion-free overload unlatching and manual switching operation is obtained.

At the high end of the range of latching angles, the ledge abutment surface 48 may have amaximum value which arises when the switchbreaker operations lose reliability. This unreliable operation occurs due to springs 38-38 which pull bimetallic element 20 against ledge 26 of latching plate 28 and spring 36 which seats the entire plunger assembly against stationary contacts 16-16. Thus, if latch angle (b is increased beyond this maximum, which generally is at about 50, springs 36, 38 and 38' may exert a sufficient force to prematurely cause bimetallic element 20 to be pulled off ledge 26. Above the maximum latch angle, a vibratory environment would be likely to cause such premature unlatching.

Other factors may influence the desired latch angle 4:. For example, the materials selected for the bimetallic element may affect the desired latch angle, since a softer higher overload current sensing material may require a greater latch angle to prevent distortion during manual switching. The latch angle of about 30 has been found suitable for ampere rated switchbreakers.

ln the embodiment as shown in FIG. 2, the other downwardly extending leg 58 of U-shaped bimetallic element is located opposite a smooth wall 60 of plunger 22. If necessary for higher current ratings, another latch plate and ledge may be operatively disposed with respect to leg 58.

The plunger 22 has an upper located shoulder 62. Since a manual pull on extension 30 could shear off shoulder 62 upon contact with housing wall 64, a stop 66 is provided. Metal extension 30, which is screwed onto insulator plunger 22 with a threaded stud 68, is cylindrical in shape and has an axially oriented slot 70 which captures stop 66. Stop 66 is in the form of a pin driven through a hole in bushing 32. The stop pin 66 is so located that the spacing B between stop pin 66 and the stop surface 72 of slot 70 is slightly smaller than the distance A between shoulder 62 and wall 64 of housing 17. Thus, when a manual switching pull is applied to extension 30 and bimetallic element 20 has been unlatched from ledge 26, a stop pin 66 rather than shoulder 62 absorbs the momentum from the unlatched plunger assembly.

The spacing C between stop pin 66 and the upper stop surface 74 exceeds the distance D between the latched and unlatched positions of bimetallic element 20 to enable a relatching by depressing extension 30 to where ledge 26 is moved just below segment 24 of bimetallic element 20.

It may thus be appreciated that a switch-breaker in accordance with the invention has a convenient and simple construction whereby a structure which was previously limited to a circuit breaking function may now also be used to provide an additional manual switch function. The latched condition between a bimetallic element and a latch plate may be manually overcome to form a reliable switch-breaker without the use of other release components such as cams, detents and the like employed in the prior art.

What is claimed is:

1. In a switch-breaker wherein a bimetallic element for sensing desired current overloads operates in a latching relationship with a latch plate and wherein a switch operation is obtained by movement along an axis of a plunger on which the latch plate is mounted, the improvement comprising a bimetallic element; and

a latch plate having an abutment ledge surface located for latching contact with the bimetallic element to establish a desired current overload sensing and circuit interrupting capability for the switchbreaker, said ledge surface being aligned along a latch plane which forms a predetermined latching angle with a plane that is transverse to the axis, said predetermined latch angle being in an angular range having a minimum value below which a manual override of the latched condition is accompanied by a distortion of the bimetallic element with a disruption of sensing of a desired overload current, said angular range further having a maximum value above which sliding separation of the latch plate and the bimetallic element in the absence of a manual switch operation may occur, with said latch plate and bimetallic element maintaining said desired current overload sensing capability of the switch-breaker within said angular range. 2. The improved switch-breaker as claimed in claim 1 wherein the range of the predetermined latch angle is between about 20 and about 50.

3. The improved switch breaker as claimed in claim 2 wherein the predetermined latch angle is about 30. 4. A switch-breaker having a desired overload current rating and an electrical switch comprising a bimetallic element and a latch plate, said bimetallic element operating in a latched condition with the latch plate to close the electrical switch, with a switch contact operated by the bimetallic element, said bimetallic element being spring loaded to open said switch upon the occurrence of a current overload condition when the bimetallic element autornatically unlatches from the latch plate, a housing and a plunger assembly movably mounted to the housing, said latch plate being mounted on the plunger assembly, said plunger assembly being spring loaded for movement along an axis to urge the latched bimetallic element to close the switch,

said latch plate having an abutment surface extending towards the bimetallic element for operative latching contact therewith, said abutment surface being aligned along a latch plane which fonns a predetermined angle with a planetransverse to the axis of movement of the plunger assembly,

said predetermined angle being within a range having a maximum value determined to inhibit spring actuated unlatching of the bimetallic element and the latch plate, said range having a minimum value below which the plunger assembly movement along said axis and against the bimetallic element is accompanied by an undesired impairment of said bimetallic element, with manual actuation of the plunger assembly within said range being effective to provide switch action of the switch breaker while maintaining the desired overload current rating.

5. The switch-breaker as claimed in claim 4 wherein said plunger assembly is provided with an actuator extension having a pair of stop surfaces spaced from one another in correspondence with desired limits of movestop being in the form of a pin mounted to the switch sleeve and extending transversely across said bore.

7. The switch breaker as claimed in claim 4 wherein 5 said range of angles is between about 20 and about 8. The switch-breaker as claimed in claim 7 wherein said angle is about 30.

i 8 i i i 

1. In a switch-breaker wherein a bimetallic element for sensing desired current overloads operates in a latching relationship with a latch plate and wherein a switch operation is obtained by movement along an axis of a plunger on which the latch plate is mounted, the improvement comprising a bimetallic element; and a latch plate having an abutment ledge surface located for latching contact with the bimetallic element to establish a desired current overload sensing and circuit interrupting capability for the switchbreaker, said ledge surface being aligned along a latch plane which forms a predetermined latching angle with a plane that is transverse to the axis, said predetermined latch angle being in an angular ranGe having a minimum value below which a manual override of the latched condition is accompanied by a distortion of the bimetallic element with a disruption of sensing of a desired overload current, said angular range further having a maximum value above which sliding separation of the latch plate and the bimetallic element in the absence of a manual switch operation may occur, with said latch plate and bimetallic element maintaining said desired current overload sensing capability of the switch-breaker within said angular range.
 2. The improved switch-breaker as claimed in claim 1 wherein the range of the predetermined latch angle is between about 20* and about 50*.
 3. The improved switch breaker as claimed in claim 2 wherein the predetermined latch angle is about 30*.
 4. A switch-breaker having a desired overload current rating and an electrical switch comprising a bimetallic element and a latch plate, said bimetallic element operating in a latched condition with the latch plate to close the electrical switch, with a switch contact operated by the bimetallic element, said bimetallic element being spring loaded to open said switch upon the occurrence of a current overload condition when the bimetallic element automatically unlatches from the latch plate, a housing and a plunger assembly movably mounted to the housing, said latch plate being mounted on the plunger assembly, said plunger assembly being spring loaded for movement along an axis to urge the latched bimetallic element to close the switch, said latch plate having an abutment surface extending towards the bimetallic element for operative latching contact therewith, said abutment surface being aligned along a latch plane which forms a predetermined angle with a plane transverse to the axis of movement of the plunger assembly, said predetermined angle being within a range having a maximum value determined to inhibit spring actuated unlatching of the bimetallic element and the latch plate, said range having a minimum value below which the plunger assembly movement along said axis and against the bimetallic element is accompanied by an undesired impairment of said bimetallic element, with manual actuation of the plunger assembly within said range being effective to provide switch action of the switch breaker while maintaining the desired overload current rating.
 5. The switch-breaker as claimed in claim 4 wherein said plunger assembly is provided with an actuator extension having a pair of stop surfaces spaced from one another in correspondence with desired limits of movements by the plunger assembly along the axis, a stop mounted to the housing for contract by said stop surfaces, said stop surfaces being spaced from said stop to inhibit destructive contact between the plunger assembly and the housing.
 6. The switch-breaker as claimed in claim 5 and further including a switch sleeve having a through bore and mounted to the housing with the bore in alignment with said axis to receive said actuator extension, with said stop being in the form of a pin mounted to the switch sleeve and extending transversely across said bore.
 7. The switch breaker as claimed in claim 4 wherein said range of angles is between about 20* and about 50*.
 8. The switch-breaker as claimed in claim 7 wherein said angle is about 30*. 